Lung Function Trajectory from Infants to Primary School Children in the Chinese Population

Abstract Background: Preterm birth impairs early lung development and may lead to long-term respiratory morbidity. This study describes lung function trajectories from infancy to early childhood in a contemporary Chinese cohort. Methods: A single-center retrospective observational study (2013–2025) of 239 infants who underwent infant lung function (ILF) testing. A subgroup had follow-up impulse oscillometry and spirometry. Results: A total of 172 infants were enrolled after inclusion and exclusion criteria. Preterm infants showed a significantly higher respiratory rate, lower Tpef/Tex, lower forced expiratory volume at 0.5 s (FEV0.5)/forced vital capacity (FVC), and the average flow from the point at which 25% of the FVC has been exhaled to the point at which 75% of the FVC has been exhaled (FEF25-75) on raised volume rapid thoracoabdominal compression (RVRTC) compared with term infants. Gestational age and birth weight positively correlated with Tpef/Tex, FEV0.5/FVC, and FEF25-75 ( r = 0.2 to 0.3). Infant Tpef/Tex, FEV0.5, and FEF25-75 negatively correlated with preschool Impulse Oscillometry System (IOS) small-airway marker zR5–R20 ( r = –0.3 to –0.4). Bronchodilator responsiveness in infancy predicted responsiveness on later IOS in 67% of cases. The original National Institute of Child Health and Human Development 2001 BPD definition was more discriminative of ILF impairment than the Jensen 2019 definition. Conclusions: In Chinese children, extreme prematurity leads to persistent obstructive deficits from infancy into early childhood. RVRTC parameters (especially FEV0.5/FVC and FEF25–75) and Tpef/Tex are useful early predictors of subsequent small-airway dysfunction.